This protocol describes research that will examine the driving abilities of elderly drivers with and without cognitive impairment related to probable or possible Alzheimer's disease. This research will expand our knowledge about cognitively impaired older drivers and extend the observations made during our present research studies from RO1#AG16335, entitled "A Longitudinal Study of Hazardous Drivers With Dementia." Specifically, we will examine 150 older drivers with mild Alzheimer's disease (N=50), questionable or mild dementia (N=50), and no cognitive impairment (N=50). We will compare performance on specific computerized measures of visual attention and executive function to digital camera recordings of subjects in their own cars, driving in their natural environments. We will perform a similar analysis of the computerized measures for the same subjects completing an extended version of the Rhode Island adaptation of the Washington University Road Test. Driving outcomes will be scored on continuous rating scales as well as global assessments of safety. These assessments will be done at baseline and repeated at one year. This will be the first study of its kind to directly examine cognitively impaired elders in their natural driving environments. We will compare driving performance in the structured road test setting to performance in the unstructured natural setting. This comparison will help us to understand the validity of the road test as a "gold standard" for driving assessment in this population. Furthermore, we will characterize and quantify the types of errors made in driving, by use of a reliable rating scale of the video recordings in both familiar and unfamiliar driving environments. We predict that video recordings in the natural environment will be more sensitive for detection of driver errors. Secondary goals of this research will include examination of the accuracy of family members and caregivers in predicting driving performance ratings by a professional driving instructor in the natural and road test settings. Relevance to public health: Ultimately, this research seeks to develop selected computerized measures for pilot testing as a screening measure in the clinician's office practice or in a department of motor vehicles. Also, we will gain much needed insight into the relevance of formal road tests to actual day to day driving performance by cognitively impaired older drivers. In this way, knowledge gained from the longitudinal study will further advance our understanding of the very important and vexing problem of drivers with early dementia, producing some potential solution to the identification of those at greatest risk for hazardous driving.